1. Field Of The Invention
The present invention relates to tamper-indicating wrappers. More particularly, this invention relates to multi-layer, laminated wrappers wherein a visible change between layers of the wrapper indicates that the wrapper has been punctured or that there has been tampering with the wrapper or its contents. The present invention also relates to bonding agents used with such wrappers.
2. Description Of Related Art
Various consumer goods are packaged in plastic wrappers for a multitude of purposes. For many consumer goods, such wrappers maintain the freshness and purity of the product. For others, the wrapper serves as a means to display the wrapped item or to present information about the item.
The use of plastic packaging materials has been greatly influenced by the recent instances of product tampering. Product tampering has led to the use of so-called tamper-proof or tamper-indicating seals for packaging consumer goods. These seals are generally applied by heat-shrinking or gluing plastic strips or plastic sheets over lids and cartons. These seals are only effective for extreme cases of tampering such as when the lid or carton is opened and the said is completely broken. The seals often cannot serve as indicators of minute ruptures or punctures, such as those made by a hypodermic needle. Additionally, for such seals to have any effectiveness, the consumer must be aware of and inspect the seal.
Various tamper-indicating structures are known. One type uses a transparent sheet that becomes opaque when subjected to stress. For example, U.S. Pat. No. 4,837,061 to Smits et al. discloses a laminated structure which delaminates when stressed, generating a color to indicate tampering. Similarly, U.S. Pat. No. 3,896,965 to Cornell discloses a tape closure with a layer containing microencapsulated color-forming material. Upon flexing, the encapsulated color-forming material is released, which generates color and indicates tampering.
Other tamper-indicating structures are made from bands of plastic material and used as security tags. For example, U.S. Pat. No. 3,463,532 to Chidley et al. discloses a tag in which dye-impregnated gauze is enclosed in a band of plastic material. The band is made so that there is an inherently weak seam extending around the length of the plastic band. Rupture of this band exposes the gauze to air and results in a tamper-indicating color change. A similar security tag is disclosed in U.S. Pat. No. 4,643,122 to Seybold. In this tag, a color change results, upon breakage of the tag and evaporation of a solvent.
U.S. Pat. No. 4,516,679 to Simpson et al. discloses another type of structure, namely a "Tamper-Proof Wrap." In this wrap, chemical layers are separated by layers of film. The chemicals may be absorbed into mats that are placed between film layers. Different constructions, such as three film layers and two mats and two film layers and one mat, are described. The chemicals may also be coated directly onto the film layers. When the wrap is punctured, the chemical layers come together to cause either a color change or the generation of heat or gas to swell, decompose, or discolor the wrap.
The most significant problem with prior tamper-indicating wrappers is that the wrappers are not transparent. As such, the usefulness of the wrappers is extremely limited. Furthermore, many of the these tamper-indicating structures are not sufficiently sensitive to detect minute ruptures or punctures such as may be made by a hypodermic needle.
Accordingly, it is an object of this invention to provide a reliable and inexpensive means of irreversibly indicating tampering with or rupture of transparent or translucent plastic packaging materials.
It is another object of this invention to provide a tamper-indicating wrapper made from materials that are substantially non-toxic and non-odorous such that the wrapper may be used with a host of consumable items such as medicines, food products, tobacco goods, and the like, and which may be applied to these consumer goods by conventional packaging methods.
It is a further object of this invention to provide a tamper-indicating wrapper made from multiple plies of packaging material in which the plies are laminated together by a substantially transparent bonding agent.
It is a still further object of this invention to provide a tamper-indicating wrapper that is sufficiently sensitive to detect minute ruptures such as those which result from penetration of the wrapper by a hypodermic needle.
It is a still further object of this invention to provide a tamper-indicating wrapper that provides consumers with an obviously apparent, easily visible change to indicate tampering.
It is a still further object of this invention to provide a bonding agent for use with ethylene vinyl alcohol films.